We hear of a bird whose chirping sounds like ‘sherakrak’ and is named accordingly. Our sages say that when the Sherakrak will chirp while sitting on the ground, it will signal the arrival of Moshiach.

Why is this bird and its particular sound going to announce the arrival of Moshiach? 
How do birds have the ability to know the future?
When is a person supposed to be a “feifer” (whistler), and when not? 

Geula and Moshiach with Rabbi Sholom Zirkind.